As i continue to get used to using my energy monitoring setup i now have power & kWh from my three CT’s (single phase, 2 on Line before & after the meter one on Neutral) and I’m tracking meter pulsecounts which i’m scaling (1000 per kWh) to give me the meter kWh usage.
Over the few days that i’ve had this running, my 3 CT’s are tracking pretty closely (within 10W), but i’m getting an ever growing divergence between the pulsecount and the CT’s - currently in the order of approx 0.5kWh for 17.5kWh usage over 24 hours.
I get the need for calibration over nominal calculated coefficients to account for manufacturing tolerances and individual setups and will be calibrating my system in due course. I am curious before i do though as to what to expect - i.e how close should i be able to get my CT / Vrms calculated kWh to the pulsecount value over the long term? Is it possible to eradicate this divergence or will there always be some drift?